1. Field of the Invention
The present invention is directed to a monolithic semi-conductor laser which emits a single light beam having blue, green and red wavelengths and which is suitable for use in transmission, processing, generating, or printing multi-wavelength-light information.
2. Description of the Prior Art
Semi-conductor lasers are known which are used in a variety of analog and digital color imaging systems. However, the colors available from the semi-conductor lasers of the prior art do not match the frequency of conventional color photographic film and paper. As a result it has been necessary to employ special films and paper which are false sensitized to the wavelengths which are available from the semi-conductor lasers or to substitute larger, bulkier, and more expensive gas lasers which can produce the desired light frequencies. However, as previously noted, such gas lasers are both expensive and bulky, reducing their usefulness in some printing operations. Moreover, none of the semiconductor or the gas lasers can provide more than a limited range of wavelengths so that a plurality of such lasers must be employed to produce a full color image. When a plurality of such light sources are utilized, it is necessary to employ complex, space-consuming, and expensive light combining systems in order to combine the various light beams into a single writing beam. Otherwise it is necessary to sequentially employ the various wavelength lasers in a plurality of passes which is both costly and time-consuming.
U.S. Pat. No. 4,993,036 discloses a semiconductor laser array which includes a plurality of lasers capable of producing coherent light having different wavelengths. However, it will be seen that the examples of the different wavelengths capable from the arrangement disclosed therein vary only between 808 nm and 869 nm, neither of which correspond to a wavelength to which conventional photographic films and papers are sensitive. Moreover, this patent discloses a laser array comprising a plurality of lasers which are spaced along the array and thus must employ additional optics to combine the various light outputs into a single beam.